The demand for rapid processing in the development of silver halide photographic materials has increased in recent years. In carrying out rapid processing, the development temperature is generally raised to shorten development time. However, when high-temperature processing (e.g., at a temperature of not lower than 40.degree. C.) is conducted, the oxidation reaction of developing solutions with air is accelerated or the developing solutions are concentrated by evaporation. As a result, the compositions of the developing solutions ar greatly changed and it is difficult to maintain the photographic characteristics of fresh solutions. Thus, this method is not preferable.
Other methods for increasing development activity in carrying out rapid processing include a method wherein the amount of developing agents is increased and a method wherein the pH of the developing solutions is increased. In the method wherein the amount of the developing agents is increased, the amount of sulfites for use in stabilizing the developing solutions must be increased and the amount of solvents for dissolving the developing agents must also be increased. Accordingly, the capacity of concentrates for preparing the developing solutions is increased. In addition, costs are increased. Hence, the application of this method is limited to a certain extent. In the method wherein the pH of the developing solutions is increased, stabilization of the developing solution is sacrificed. For the above-described reasons, there is a high need to accelerate the rate of development and increase the effective sensitivity of developed light-sensitive materials without raising development temperature, increasing costs and the capacity of concentrates for the developing solutions and without sacrificing the stabilization of the developing solutions. For this purpose, various development accelerators are commonly used.
Examples thereof include thioether compounds. The details thereof are described in L. F. A. Mason, Photographic Processing Chemistry, page 44 (1975 London, Focal Press), JP-A-58-221843 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), JP-A-51-90822, JP-A-51-89732, JP-A-49-90536 and JP-A-53-30331. The thioether compounds have an effective development accelerating function, but development is accelerated by dissolving silver halide, that is, by utilizing dissolving physical development. As a result, silver stain in the developing solutions is increased, the staining of the development rack and rollers of automatic processors is promoted, and the light-sensitive materials are marred and stained. The frequency of inspection for the maintenance of the automatic processors must be increased. Hence, the thioether compounds are not preferable from the viewpoint of practical use.
Typical methods for imparting high sensitivity and high contrast to silver halide light-sensitive materials include the methods wherein polyethylene glycols are used. The details thereof are described in U.S. Pat. Nos. 2,400,532, 2,848,830, 2,944,900, 3,385,708, 3,671,247 and 3,947,273.
The methods using polyethylene glycols are very effective in processing light-sensitive materials having silver halide emulsion layers containing commonly used silver halide grains such as spherical grains or cubic grains. However, the methods have the problem that graininess becomes poor, and hence these methods are of no practical use.
Further, the methods using polyethylene glycols are hardly effective in processing light-sensitive materials having silver halide emulsion layers comprising tabular grains which are considered to have a high covering power and to be advantageous in conducting rapid processing.
Accordingly, there is a demand for a method for effectively sensitizing silver halide photographic materials without reducing image quality.